Cerebral edema solute catheter and method of draining cerebral edema

ABSTRACT

Catheters for removing interstitial fluid from a cerebral edema that comprises an edema drainage section terminating in a proximal tip linked to a fluid transport section terminating in a distal tip are disclosed. The edema drainage section comprises an outer wall, an inner drainage tube and an intermediate solute compartment that comprises a solute. Methods of removing fluid from a cerebral edema of an individual are disclosed, and comprise the steps of inserting the edema drainage section of the catheter into communication with the fluid of the cerebral edema and inserting the fluid transport section of the catheter into a fluid receptacle or the individual&#39;s peritoneal cavity. The fluid is drawn into the edema drainage section and emerges from the distal tip of the fluid transport section of the catheter.

FIELD OF THE INVENTION

The present invention relates to solute drainage catheters and, inparticular, to a catheter for draining interstitial fluid from acerebral edema.

BACKGROUND OF THE INVENTION

Cerebral edema is a type of brain swelling most commonly associated withcerebral trauma or mass lesions, which results in an increase in volumeof intracranial contents leading to serious, and sometimes fatal,intracranial pressure. Interstitial (extracellular) fluid, or freewater, is abnormal in the brain and accumulates as a result of swellingfrom a nearby brain tumor, or other type of cerebral lesion. This fluidenters the white matter in the brain due to a compromise of theblood-brain barrier. The fluid can contain small proteins, as well asother small molecular weight molecules, which escape the circulatorysystem or are a result from the tissue damage itself.

Currently, there is no known approach for removing or draininginterstitial fluid from a cerebral edema. Methods exist only forimproving the symptoms of swelling due to the accumulation of the fluid.These methods involve the use of oral or intravenous steroids, whichhave known systemic side effects. For example, the steroid DECADRON™ hasonly a modest effect on cerebral edema and has systemic side effectsincluding water retention, osteoporosis, aseptic necrosis of the femoralhead, capillary fragility with easy bruising, increased appetite, andinsomnia.

Prior art fluid draining systems only teach removing cerebrospinalfluid, and other fluids, from ventricles in the brain. These drainingsystems consist of a shunt which protrudes into the ventricular region,such as a typical catheter described in U.S. Pat. No. 4,215,695, issuedto Spitz, et al. In such prior art catheters, the pressure of thecranial cavity serves as the mechanism which moves the cerebrospinalfluid through the catheter to an extracorporeal collection area or otherregion within the patient's body for disposal. However, sufficientpressure is not present in the region of a cerebral edema to provide forthis type of mechanism for transporting interstitial fluid through aventricle type shunt placed in the region.

Accordingly, a need exists for such an apparatus for draininginterstitial fluid from a cerebral edema. The cerebral edema catheterdescribed below provides for the drainage of interstitial fluid from acerebral edema.

SUMMARY OF THE INVENTION

The present invention is directed to a catheter for removinginterstitial fluid from a cerebral edema. The catheter, which isreferred to herein as a cerebral edema solute catheter or CES catheter,has an edema drainage section and a transport section. The edemadrainage section terminates in a proximal tip. The fluid transportsection terminates in a distal tip. The edema drainage section may belinked directly to the transport section or indirectly by intermediatecomponents such as a connector, such that one end of the connector islinked to the edema drainage section and the other end of the connectoris linked to the transport section.

The CES catheter may be used as follows. The edema drainage section isinserted into the patient's brain and comes into contact with theinterstitial fluid. The fluid enters the edema drainage section,progresses through it and into the transport section. The fluid entersthe edema drainage section by first passing through the pores, openingsor openings of the outer wall and entering the intermediate solutecompartment. The fluid hydrates the solute and passes from theintermediate solute compartment into the inner drainage tube throughpores or openings of the inner drainage tube. The fluid passes throughthe inner drainage tube and into the transport section. The fluid eithercollects in a fluid receptacle or is discharged into the patient's body.The fluid receptacle may be linked directly to the transport section orlinked by way of a junction. The fluid receptacle may be calibrated tomeasure the amount of fluid drained.

The edema drainage section is inserted into the patient's brain at thesite of the edema and comes into contact with the fluid. The edemadrainage section has an outer wall, an intermediate solute compartmentand an inner drainage tube. The edema drainage section of the CEScatheter is inserted into the patient's brain and is positioned to thesite in the brain in order to come into contact with the fluid to beremoved.

The outer wall of the drainage section is attached at one end directlyor indirectly to the transport section. In some embodiments, the outerwall is attached to a connector which is linked to the transportsection. In one embodiment of the invention, the outer wall is eitherporous, such that it has a molecular weight exclusion limit, or itcontains an opening so fluid can pass through it and come in contactwith the intermediate solute compartment. When the edema drainagesection of the CES catheter is inserted into the patient's brain, theouter wall comes into contact with the fluid to be removed. The fluidpasses through the pores of, or opening or openings in the outer walland comes into contact with the intermediate solute compartment.

The intermediate solute compartment separates the inner surface of theouter wall and the outer surface of the inner drainage tube, andcontains a solute. The solute can be free, or can be contained within asolute compartment membrane. The solute compartment membrane is porousand preferably is a micropore structure such that water, or fluid, fromthe edematous area of the brain is able to pass through the solutecompartment membrane and into the solute.

The solute comprises large molecular weight macromolecules which areunable to pass through the outer wall and/or the solute compartmentmembrane and which are capable of being hydrated. Such macromoleculescreate an osmotic diffusion gradient such that water is drawn into theedema drainage section of the CES catheter through the outer wall at theproximal tip.

The inner drainage tube is a porous, membranous, tube within the CEScatheter and surrounded by the outer wall and intermediate solutecompartment. In one embodiment of the invention, the inner drainage tubecomprises three flanges that radiate from the proximal tip portion ofthe drainage section and longitudinally traverse the outer wall, thusfirming the supporting framework for the outer wall where the outer wallcomprises a porous material. The outside of the inner drainage tube issurrounded by the solute compartment membrane or by the solute itself.The area between the outer surface of the inner drainage tube and theouter wall forms the intermediate solute compartment. The inner drainagetube preferably is a water permeable membrane that transports smallmolecules, such as water, into the lumen of the drainage tube. While notwishing to be bound by theory, this transport of fluid arises fromhydrostatic pressure building up in the intermediate solute compartment.Interstitial fluid, which is drawn through the outer wall and hydratesthe solute, passes through the pores of and enters into the innerdrainage tube. The inner drainage tube extends through the edemadrainage section and may empty directly into the fluid transportsection.

The fluid transport section is essentially a tube connected directly orindirectly to the edema drainage section.

The present invention is also directed to a method of removing fluidfrom a cerebral edema of an individual comprising the steps of insertingthe edema drainage section of the cerebral edema solute catheter of theinvention into communication with the fluid of the cerebral edema, andinserting the fluid transport section of the cerebral edema solutecatheter of the invention into a fluid receptacle or the individual'speritoneal cavity, wherein the fluid is drawn into the edema drainagesection and emerges from the distal tip of the fluid transport sectionof the cerebral edema solute catheter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are views of preferred embodiments of the cerebral edemasolute catheter. FIG. 1C shows a cross sectional view of the cerebraledema solute catheter show in FIG. 1B.

FIGS. 2A, 2B, 2C, 2D, and 2E show several embodiments of the proximaltip of the cerebral edema solute catheter.

FIG. 3 is a view of the embodiment set forth in FIG. 1A in which theproximal tip of the catheter is in an area of the brain to be drained.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is directed to a cerebral edema solute catheter(CES catheter) which provides for the drainage of interstitial fluidfrom a cerebral edema. The cerebral edema solute catheter 10 shown inFIGS. 1A and 1B comprises three regions or sections. The CES catheter 10comprises a first section, the edema drainage section 11, which drainsthe fluid from the cerebral edema within the brain The terminal regionof the edema drainage section 11 comprises a proximal tip 16 of thecerebral edema solute catheter 10. The CES catheter 10 also comprises asecond portion, a fluid transport section 12, which transports the fluidfrom the edema drainage section 11 of the CES catheter 10 to areceptacle or another region of the body. The terminal region of thefluid transport section 11 comprises a distal tip 17 of the cerebraledema solute catheter 10. The CES catheter 10 may optionally comprise athird section, a connector section 13, which connects the edema drainagesection 11 of the CES catheter 10 to the fluid transport section 12 ofthe CES catheter 10.

The edema drainage section 11 of the cerebral edema solute catheter 10comprises an outer wall 14, which forms a tube or tube-like structure.The outer wall 14 can be manufactured from a variety of medicallyaccepted plastics or metals, as is well known to those skilled in theart. A preferred plastic is silastic plastic. Such an embodiment whereinthe outer wall comprises a silastic plastic is shown in FIG. 1A. Thethickness of the outer wall 14 is between 0.001 and 5.0 mm, preferablybetween 0.01 and 3.0 mm, and more preferably between 0.1 and 1.0 mm. Thetube formed by the outer wall 14 can be of uniform diameter throughoutthe length of the edema drainage section 11 of the cerebral edema solutecatheter 10. Alternately, the tube formed by the outer wall 14 can betapered or enlarged at either end of the edema drainage section 11.

In another embodiment of the invention, as shown in FIG. 1B, the outerwall 14 comprises a porous membrane, such as, for example, dialysistubing, as is well known to those skilled in the art of dialysis. Apreferred membrane is SPECTRAPORE™. The porous membrane which comprisesthe outer wall 14 preferably is a micropore structure such that water,or fluid, from the edematous area of the brain is able to pass throughthe outer wall 14 and into the CES catheter 10. Thus, the porousmembrane of the outer wall 14 preferably has a molecular weightexclusion limit which is greater than the molecular weight of the fluidto be drained from the cerebral edema. Preferably, the molecular weightexclusion limit of the porous membrane of the outer wall 14 excludespassage of molecules having molecular weights greater than 80,000, morepreferably greater than 40,000, and most preferably greater than 12,000.The porous membrane of the outer wall 14 is preferably dialysis tubingwith a molecular weight exclusion limit of between about 12,000 and14,000. In this embodiment, the outer wall 14 is supported as discussedbelow. The tube formed by the outer wall 14 in this embodiment can be ofuniform diameter throughout the length of the edema drainage section 11of the cerebral edema solute catheter 10. Alternately, the tube formedby the outer wall 14 can be tapered or enlarged at either end of theedema drainage section 11. Preferably, the outer wall 14 of thisembodiment is a rounded triangle in cross-section. In either embodimentof the invention, the diameter of the tube formed by the outer wall 14is between 1.0 mm and 4.0 cm, preferably between 5.0 mm and 3.0 cm, andmore preferably between 1.0 cm and 2.0 cm. In addition, the edemadrainage section 11 is preferably from about 1.0 cm to about 30.0 cm,more preferably from about 5.0 cm to 20.0 cm, and most preferably isadapted to be an optimum length determined by the distance from thelocation of the cerebral edema to the outer surface of the skull.

The edema drainage section 11 of the cerebral edema solute catheter 10also comprises, inside of the tube formed by the outer wall 14, an innerdrainage tube 15. Preferably, the inner drainage tube 15 is a singletube. Alternately, the inner drainage tube 15 can be comprised of aplurality of inner drainage tubes. The inner drainage tube 15 can becentrally located within the edema drainage section 11 of the cerebraledema solute catheter 10, or, alternately, peripherally located withinthe edema drainage section 11 of the cerebral edema solute catheter 10,such as, for example, in contact with the outer wall 14. The innerdrainage tube 15 preferably is a water permeable membrane, such as, forexample, hollow fiber tubing produced by AMICON™. Alternately, the innerdrainage tube 15 can be made of other membranes, such as, for example,water permeable membranes. The inner drainage tube 15 preferably onlyallows transport of small molecules, such as water, into the lumen ofthe inner drainage tube 15. Preferably, the inner drainage tube 15extends only through the entire length of the edema drainage section 11of the cerebral edema solute catheter 10, however, the inner drainagetube 15 may only partially extend through the edema drainage section 11.Alternately, the inner drainage tube 15 can extend into the fluidtransport section 12 of the cerebral edema solute catheter 10 or into anintermediate component which is linked to the fluid transport section 12of the cerebral edema solute catheter 10, such as a connector section 13which is linked to the fluid transport section 12 of the cerebral edemasolute catheter 10. The thickness of the wall of the inner drainage tube15 is preferably between 0.001 and 1.0 mm, and more preferably between0.01 and 0.1 mm. The diameter of the inner drainage tube 15 ispreferably between 1.0 mm and 2.0 cm, and more preferably between 5.0 mmand 1.0 cm. The inner drainage tube 15 can be of uniform diameterthroughout the length of the edema drainage section 11 of the cerebraledema solute catheter 10. Alternately, the inner drainage tube 15 can betapered or enlarged at either end of the edema drainage section 11 ofthe CES catheter 10. In some embodiments of the invention, the innerdrainage tube 15 is closed at the proximal tip 16. That is, the lumen ofthe inner drainage tube 15 at the proximal tip 16 of the edema drainagesection 11 of the CES catheter 10 is not in contact with the edema. Inalternate embodiments, the inner drainage tube 15 is open.

In another embodiment of the invention, as shown in FIG. 1B, the innerdrainage tube 15 comprises a plurality, preferably three, of flanges 35.The flanges 35 may be comprised of a silastic plastic or the like. Theflanges 35 are either continuous with the inner drainage tube 15, oralternately, the flanges 35 are connected to the inner drainage tube bya variety of means well known to the skilled artisan. FIG. 1C shows across sectional view of the edema drainage section 11 of the CEScatheter as shown in FIG. 1B, showing the inner drainage tube 15, theouter wall 14, and the flanges 35. In this embodiment, the area betweenthe flanges 35 creates the intermediate solute compartment 21, which isfilled with solute 18 (not shown). The flanges 35 form the supportingframework for the outer wall 14, wherein the outer wall 14 comprises aporous membrane. The outer wall 14 is connected to the flanges 35 byconventional means known to those skilled in the art.

The edema drainage section 11 of the cerebral edema solute catheter 10also comprises, in the space between the outer wall 14 of the edemadrainage section 11 and the inner drainage tube 15, an intermediatesolute compartment 21 that contains a solute 18. The solute 18 is eitherexists free within the intermediate solute compartment 21, and thus isencompassed by the outer wall 14, or is enclosed within an intermediatesolute compartment membrane 19. The intermediate solute compartmentmembrane 19 preferably is a micropore structure such that water, orfluid, from the edematous area of the brain is able to pass through theintermediate solute compartment membrane 19 and into the solute 18.Thus, the intermediate solute compartment membrane 19 preferably has amolecular weight exclusion limit which is greater than the molecularweight of the fluid to be drained from the cerebral edema. Preferably,the molecular weight exclusion limit of the intermediate solutecompartment membrane 19 excludes passage of molecules having molecularweights greater than 80,000, more preferably greater than 40,000, andmost preferably greater than 12,000. The intermediate solute compartmentmembrane 19 is preferably dialysis tubing with a molecular weightexclusion limit of between about 12,000 and 14,000. Preferably, theintermediate solute compartment membrane 19 comprises the same porousmembrane as the porous membrane of the outer wall 14 in some embodimentsof the invention, such as the embodiment shown in FIG. 1B.

The solute 18 comprises large molecular weight macromolecules which arecapable of being hydrated. Such macromolecules create an osmoticdiffusion gradient such that water is drawn into the edema drainagesection 11 of the CES catheter 10 through the proximal tip 16, orthrough the outer wall 14 comprising a porous membrane, or through acombination thereof. Preferably, the molecular weight of the solute 18is from 100,000 to 1,000,000, more preferably from 300,000 to 750,000,and most preferably is 500,000. The solute 18 can be, for example,agarose, cellulose, polystyrene, proteins, dextran, apoferritin, orother large molecular weight macromolecules, or a combination thereof.Preferably, the solute 18 is dextran or apoferritin. Preferably thesolute 18 is in a 1% to 50% solution with water, and most preferably isin a 10% solution. The most preferred solute 18 is a 10% solution ofdextran having a molecular weight of 500,000. The solute 18 has amolecular weight such that is it unable to pass through the intermediatesolute compartment membrane 19 and/or the openings or pores of the outerwall 14 and inner drainage tube 15.

The intermediate solute compartment 21, and thus the solute 18 andintermediate solute compartment membrane 19, preferably extend throughthe entire length of the edema drainage section 11 of the cerebral edemasolute catheter 10. However, it is contemplated that the intermediatesolute compartment 21 may only be partially filled with the intermediatesolute compartment membrane 19 containing the solute 18. Theintermediate solute compartment 21 is located peripherally to the innerdrainage tube 15. However, it is conceived that only the terminalsection of the edema drainage section 11 of the CES catheter 10 maycomprise the intermediate solute compartment 21. Alternately, theintermediate solute compartment 21 can extend into the optionalconnector section 13 or through the connector section 13 and into thefluid transport section 12 of the cerebral edema solute catheter 10.Preferably, the intermediate solute compartment 21 is filled with thesolute 18 such that there is no space between the intermediate solutecompartment 21 and the outer wall 14 or between the intermediate solutecompartment 21 and the inner drainage tube 15. That is, preferably, theintermediate solute compartment 21 is filled with solute 18 so as toforce the solute 18 or solute compartment membrane 19 to be in contactwith both the outer wall 14 and the drainage tube 15. However, suchspaces can exist as a result of, for example, incompletely filling theintermediate solute compartment 21 with solute 18. It is preferred thatthe solute 18 within the intermediate solute compartment 21 is within anintermediate solute compartment membrane 19 and that the intermediatesolute compartment membrane 19 is continuous and thus forms anintermediate solute compartment 21 entirely encompassing the solute 18.To this end, it can be necessary to seal both ends of the solutecompartment membrane 19 when, for example, dialysis tubing is used.Sealing the ends of the dialysis tubing can be accomplished, forexample, by clamping means, heat-sealing means, or other forms ofsealing known to those skilled in the art.

The edema drainage section 11 of the CES catheter 10 terminates at theproximal tip 16. By "proximal" is meant the tip of the CES catheter 10closest to the cerebral edema. The proximal tip 16 can take the form ofseveral structural designs, as shown in FIGS. 2A, 2B and C, all of whichprovide for contact between the cerebral edematous tissue and the CEScatheter 10. In a first embodiment, shown in FIG. 2A, the intermediatesolute compartment membrane 19 containing the solute 18 is flush withthe proximal tip 16, in which the opening of the proximal tip 16 is at aright angle with the outer wall 14. That is, the intermediate solutecompartment membrane 19 does not protrude beyond the outer wall 14 ofthe edema drainage section 11 of the CES catheter 10. In thisembodiment, the inner drainage tube 15 is also flush with the proximaltip 16. This type of proximal tip 16 is referred to as a flush proximaltip.

In another embodiment of the invention, shown in FIG. 2B, the proximaltip 16 is beveled, such as, for example, in a syringe needle. Theproximal tip 16 in this embodiment can be angled at any desirable angle.The inner drainage tube 15 can extend beyond the opening created by thebeveled proximal tip 16, or, alternately, can be flush with the opening.The inner drainage tube 15 can also be beveled in a similar manner tothat of the proximal tip 16. In addition, the intermediate solutecompartment membrane 19 containing the solute 18 is flush with thebeveled proximal tip 16. This type of proximal tip 16 is referred to asa beveled proximal tip.

In another embodiment of the invention, shown in FIG. 2C, theintermediate solute compartment membrane 19 containing the solute 18extends beyond the proximal tip 16. The proximal tip 16 can be such thatthe opening of the proximal tip 16 is at a right angle with the outerwall 14, as in FIG. 2A, or, alternately, the proximal tip 16 can bebeveled, such as in FIG. 2B. In any case, the intermediate solutecompartment membrane 19 containing the solute 18 can form a bulb-likeprojection extending beyond the outer wall 14. The intermediate solutecompartment membrane 19 preferably extends beyond the outer wall 14 frombetween about 0.1 mm and 10.0 cm, more preferably from between about 1.0mm and 2.0 cm, and most preferably between about 1.0 mm and 1.0 cm. Theinner drainage tube 15 can extend as far as the intermediate solutecompartment membrane 19, such that the inner drainage tube 15 is flushwith the end of the intermediate solute compartment membrane 19.Alternately, the inner drainage tube 15 terminates within the bulb-likeregion of the intermediate solute compartment membrane 19, or remainsflush with the end of the outer wall 14. A proximal tip 16 having any ofthese types of configurations is referred to as bulb proximal tip.

In other embodiments of the invention, any of the proximal tipsheretofore described can be perforated with drainage vents 20 within theouter wall 14, as illustrated in FIG. 2D. The drainage vents 20 can beof any shape or size such that the integrity of the outer wall 14 ismaintained. The drainage vents 20 can be within the outer wall 14 alongthe entire length of the edema drain section 11 of the catheter 10, or,alternatively, can be restricted to the terminal region of the edemadrainage section 11.

In another embodiment of the invention, shown in FIG. 2E, the proximaltip 16 of the CES catheter 10 comprises a cap 45. Such a proximal tip 16embodiment is preferably used in connection with the embodiment of theCES catheter as shown in FIG. 1B. The cap 45 preferably is comprised ofa silastic plastic, such as the same material as comprises the flanges35, as set forth above. The cap 45 is incorporated in and is continuouswith the flanges 35 of the inner drainage tube 15 (not shown).Alternately, the cap 45 is a separate piece and is attached to theflanges 35 and outer wall 14 by conventional means well known to theskilled artisan. In embodiments of the catheter, such as the embodimentshown in FIG. 1B, where the outer wall 14 comprises a porous membraneand the solute 18 is free within the intermediate solute compartment 21,cap 45 is preferred. However, in embodiments of the catheter, such asthe embodiment shown in FIG. 1B, where the outer wall 14 comprises aporous membrane and the solute 18 is within the intermediate solutecompartment 21 but enclosed within a intermediate solute compartmentmembrane 19, any of the embodiments of FIGS. 2A, 2B, or 2C can be used.A proximal tip 16 having the type of configuration shown in FIG. 2E isreferred to as a cap proximal tip.

The edema drainage section 11 of the CES catheter 10 may be connected toa connector section 13 at the end of the edema drainage section 11distal to the proximal tip 16. The connector section 13 connects theedema drainage section 11 of the CES catheter 10 to the fluid transportsection 12 of the CES catheter 10 such that the fluid drained from thecerebral edema passes from the edema drainage section 11 through theconnector section 13 and into the fluid transport section 12. Theconnector section 13 can form any angle connecting the edema drainagesection 11 and the fluid transport section 12. Preferably, the connectorsection forms a 90° angle. The connector section 12 of the CES catheter10 can be a separate piece distinct from either the edema drainagesection 11 or the fluid transport section 12. In this case, theconnector section 13 can comprise female or male sections such that theconnector section 13 screws into the appropriate end of either the edemadrainage section 11 or the fluid transport section 12, which alsocomprise a female or male counterpart, as needed. In an alternateembodiment, the inside diameter of the connector section 12 is such thatthe connector section slips over the ends of the edema drainage section11 or the fluid transport section 12. Alternately, the outside diameterof the connector region is such that it slips inside the ends of theedema drainage section 11 or the fluid transport section 12. A sealercan be used in these cases to provide for additional sealing. In anotherembodiment of the invention, the connector section 13 of the catheter 10is formed continuously with either or both of the edema drainage section11 and the fluid transport section 12. That is, the connector section 13is not a separate and distinct piece of the catheter 10.

The fluid transport section 12 of the CES catheter 10 is attached to theconnector section 13 as described above. The fluid transport section 12also comprises a catheter wall 22, which forms a tube, as in the case ofthe edema drainage section 11. The catheter wall 22 of the fluidtransport section 12 can be manufactured from a variety of medicallyaccepted plastics or metals, as is well known to those skilled in theart. A preferred plastic is silastic plastic. The thickness of thecatheter wall 22 is between 0.001 and 5.0 mm, preferably between 0.01and 3.0 mm, and more preferably between 0.1 and 1.0 mm. The diameter ofthe tube formed by the catheter wall 22 is between 1.0 mm and 4.0 cm,preferably between 5.0 mm and 3.0 cm, and more preferably between 1.0 cmand 2.0 cm. The tube formed by the catheter wall 22 can be of uniformdiameter throughout the length of the fluid transport section 12 of thecerebral edema solute catheter 10. Alternately, the tube formed by thecatheter wall 22 can be tapered or enlarged at either end of the fluidtransport section 12. The fluid transport section 12 is preferably fromabout 1.0 cm to about 200.0 cm, more preferably from about 50.0 cm to150.0 cm, and most preferably is adapted to be an optimum lengthdetermined by the distance from the connector section 13 to theperitoneal cavity of a patient.

The fluid transport section 12 terminates at a distal tip 17. The distaltip 17 can be of the same diameter as the fluid transport section 12 orcan be expanded or reduced. In a preferred embodiment of the invention,the distal tip 17 empties the fluid from the cerebral edema into theperitoneal cavity. In another embodiment of the invention, the distaltip 17 of the fluid transport section 12 of the CES catheter 10 isconnected to a shunt (not shown) in the abdominal wall of a patient,which in turn is further connected to a distensible storage compartment(not shown), such as, for example, a colostomy bag, which can be emptiedas needed.

The cerebral edema solute catheter 10 is preferably used in humans,although the catheter can also be used in a variety of other mammals.The apparatus of the present invention can be used to drain interstitialfluid from a cerebral edema. The CES catheter 10 is inserted into thebrain of an individual comprising an edema The skull of an individual isopened and the edema located using routine surgical procedures known tothose skilled in the art. The edema drainage section 11 of the CEScatheter 10 is inserted into the brain such that the proximal tip 16 isplaced into the edematous mass. Thus, the proximal tip 16 is incommunication with the fluid to be drained. An enlarged view of theedema drainage section 11 of the CES catheter 10 inserted into theedematous fluid, or interstitial fluid, 8 of the brain 40 is shown inFIG. 3. The connector section 13 is located at the outside layer of theskull 30 and is connected to the fluid transport section 12 of the CEScatheter 10 which in turn is located between the skull 30 and theoverlying scalp tissue 50. The fluid transport section 12 of the CEScatheter 10 is fed, between the skull and the scalp by routine surgicaltechniques, preferably behind the ear into the neck and through thechest section of the individual to the peritoneal cavity. Alternateroutes of placement can be used as known to those skilled in the art. Itis understood that any embodiment of the CES catheters described hereincan be used in the methods of removing fluid from cerebral edemasdescribed herein.

The concentration gradient of the solute 18 within the intermediatesolute compartment membrane 19 or free within the intermediate solutecompartment 21 creates an osmotic gradient such that the fluid from theedema is drawn into the edema drainage section 11 of the CES catheter10. The fluid passes through the outer wall 14 or the intermediatesolute compartment membrane 19, or both, and hydrates the solute 18. Theinflux of fluid from the edema into the area of the solute 18 causes anexpansion of the solute 18 until a maximum expansion is achieved, atwhich time the pressure within the edema drainage section 11 of thecatheter 10 causes the fluid to pass from the intermediate solutecompartment 21 into the inner drainage tube 15. Thus, the fluid passesfrom the edema to the inside of the edema drainage section 11 of thecatheter 10 as a result of the osmotic gradient facilitated by thesolute 18. The inner drainage tube 15 then acts as a release mechanismin which the fluid is able to be drained from the edema drainage section11 of the CES catheter 10. The fluid then passes through the innerdrainage tube 15, into the connector section 13, and into the fluidtransport section 12, where it emerges from the distal tip 17 and intothe peritoneal cavity. Thus, the CES catheter 10 as depicted in FIG. 1is a self-contained system that will continually drain interstitialfluid or free water from the edematous tissue of the brain of a patientinto another body compartment for disposal.

From the foregoing it can be seen that the present invention is directedto a catheter for draining interstitial fluid or free water from acerebral edema. It is understood that changes may be made to theembodiments described above without departing from the broad inventiveconcepts thereof. Accordingly, this invention is not limited to theparticular embodiments disclosed, but is intended to cover allmodifications that are within the scope and spirit of the invention.

What is claimed is:
 1. A catheter for removing fluid from a cerebraledema comprising:an edema drainage section terminating in a proximal tipthat is constructed and arranged to be positioned within an area ofcerebral edema, said edema drainage section comprising:an outer wall; aninner drainage tube surrounded by said outer wall; and an intermediatesolute compartment positioned immediately adjacent to said proximal tipand surrounding said inner drainage tube, wherein said intermediatesolute compartment comprises an intermediate solute compartment membranecontaining a solute comprising large molecular weight macromolecules;and a fluid transport section linked to said edema drainage section,whereby said fluid transport section terminates in a distal tip.
 2. Thecatheter of claim 1 wherein said edema drainage section is linked tosaid fluid transport section by a connector section.
 3. The catheter ofclaim 1 wherein said proximal tip is selected from the group consistingof a flush proximal tip, a beveled proximal tip, and a bulb proximaltip.
 4. The catheter of claim 3 wherein:said intermediate solutecompartment membrane has a molecular weight exclusion limit greater thanthe molecular weight of the fluid of said cerebral edema; said innerdrainage tube is a water permeable membrane; and said solute compriseslarge molecular weight macromolecules capable of being hydrated andhaving a molecular weight greater than the molecular weight exclusionlimit of said solute compartment membrane.
 5. The catheter of claim 4wherein:said solute compartment membrane has a molecular weightexclusion limit greater than 12,000; said inner drainage tube is hollowfiber tubing; and said solute is a macromolecule having a molecularweight from 100,000 to 1,000,000.
 6. The catheter of claim 5wherein:said intermediate solute compartment membrane is dialysistubing, and said solute is selected from the group consisting ofagarose, cellulose, polystyrene, proteins, dextran, apoferritin, andother large molecular weight macromolecules, or a combination thereof.7. The catheter of claim 6 wherein said solute is a 10% solution ofdextran having a molecular weight of 500,000.
 8. The catheter of claim 1wherein:said outer wall is a porous membrane; and said inner drainagetube further comprises a plurality of flanges supporting said outerwall.
 9. The catheter of claim 8 wherein:said edema drainage section islinked to said fluid transport section by a connector section; saidporous membrane has a molecular weight exclusion limit greater than themolecular weight of the fluid drained from the cerebral edema; saidinner drainage tube is a water permeable membrane; and said solutecomprises large molecular weight macromolecules capable of beinghydrated and having a molecular weight greater than the molecular weightexclusion limit of said porous membrane.
 10. The catheter of claim 9wherein:said porous membrane has a molecular weight exclusion limitgreater than 12,000; said inner drainage tube is hollow fiber tubing;and said solute is a macromolecule having a molecular weight from100,000 to 1,000,000.
 11. The catheter of claim 10 wherein:said porousmembrane is dialysis tubing, and said solute is selected from the groupconsisting of agarose, cellulose, polystyrene, proteins, dextran,apoferritin, and other large molecular weight macromolecules, or acombination thereof.
 12. The catheter of claim 11 wherein said solute isa 10% solution of dextran having a molecular weight of 500,000.
 13. Ashunt and a catheter for removing fluid from a cerebral edemacomprising:an edema drainage section terminating in a proximal tip thatis constructed and arranged to be positioned within an area of cerebraledema, said edema drainage section comprising:an outer wall; an innerdrainage tube surrounded by said outer wall; and an intermediate solutecompartment positioned immediately adjacent to said proximal tip andsurrounding said inner drainage tube, wherein said intermediate solutecompartment comprises an intermediate solute compartment membranecontaining a solute; and a fluid transport section linked to said edemadrainage section, whereby said fluid transport section terminates in adistal tip connected to said shunt; wherein said shunt is furtherconnected to a distensible storage compartment.